To upgrade and install the latest macOS update on your Mac machine, you can easily get it within the system's Software Update option. At this point you can either set it up completely fresh, or connect a backup drive and use setup assistant to migrate data.Step 2. When done, you should see the initial setup screen (choose your language).ġ4. The Mac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Once the erase is done, quit disk utility and RE-OPEN the OS installerġ2.

Erase to 'Mac OS extended, journaling enabled, GUID partition format'ġ1. Click on the drive and then click 'erase'.ġ0. The 'topmost' item should be the physical drive inside.ĩ. VERY IMPORTANT: in disk utility, go to the view menu and choose 'show ALL devices'. It will probably boot to the OS installer. The Mac should boot from the flashdriveĥ.

Select the USB drive with the pointer and hit return.Ĥ.

Press the power on button and then IMMEDIATELY hold down the OPTION key and KEEP HOLDING IT DOWN.ģ. NOTE: you could TRY the special version of internet recovery to see whether it offers you Low Sierra or High Sierra.ġ. my guess is the ONLY WAY you can install High Sierra (OS 10.13) is by using a bootable USB flash drive (which you say that you already have). The special version of internet recovery (command-SHIFT-OPTION-R) will offer you 'Low Sierra' (OS 10.12), because that's what the 2017 iMacs originally shipped with. Internet recovery (command-OPTION-R) will offer you the most recent OS that will run on a 2017 iMac. Having said that, you probably can't install High Sierra using internet recovery either. You can't use 'the recovery partition' to install High Sierra, because you can't erase the ENTIRE DRIVE from the recovery partition. My reply is based upon the premise that you don't care about anything that's on the drive NOW. Is there a complete step on how can I resolve this issue of being unable to erase the partition? My aim is to be able to install MacOS High Sierra in clean mode. 'I was also able to create a USB installer for this and the MacOS Sierra can still be used without issue.

Clean install macos high sierra